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authorLi Zefan <lizf@cn.fujitsu.com>2009-03-27 10:20:09 +0800
committerIngo Molnar <mingo@elte.hu>2009-03-31 17:27:45 +0200
commit17ba97e347bec9bbc47a0877c7a098708982129d (patch)
treeb6a7472c354e4135f1ea47482d19ae277be65dee
parent35ac51bfe4c293b67ce9f85082ba0b9bc6123c40 (diff)
blktrace: fix blk_probes_ref chaos
Impact: fix mixed ioctl and ftrace-plugin blktrace use refcount bugs ioctl-based blktrace allocates bt and registers tracepoints when ioctl(BLKTRACESETUP), and do all cleanups when ioctl(BLKTRACETEARDOWN). while ftrace-based blktrace allocates/frees bt when: # echo 1/0 > /sys/block/sda/sda1/trace/enable and registers/unregisters tracepoints when: # echo blk/nop > /debugfs/tracing/current_tracer or # echo 1/0 > /debugfs/tracing/tracing_enable The separatation of allocation and registeration causes 2 problems: 1. current user-space blktrace still calls ioctl(TEARDOWN) when ioctl(SETUP) failed: # echo 1 > /sys/block/sda/sda1/trace/enable # blktrace /dev/sda BLKTRACESETUP: Device or resource busy ^C and now blk_probes_ref == -1 2. Another way to make blk_probes_ref == -1: # plugin sdb && mount sdb1 # echo 1 > /sys/block/sdb/sdb1/trace/enable # remove sdb This patch does the allocation and registeration when writing sdaX/trace/enable. Signed-off-by: Li Zefan <lizf@cn.fujitsu.com> Acked-by: Jens Axboe <jens.axboe@oracle.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
-rw-r--r--kernel/trace/blktrace.c15
1 files changed, 7 insertions, 8 deletions
diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index 5b28f0f119c..8d6bd12aab1 100644
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -478,7 +478,7 @@ int do_blk_trace_setup(struct request_queue *q, char *name, dev_t dev,
goto err;
}
- if (atomic_add_return(1, &blk_probes_ref) == 1)
+ if (atomic_inc_return(&blk_probes_ref) == 1)
blk_register_tracepoints();
return 0;
@@ -1091,8 +1091,6 @@ static void blk_tracer_print_header(struct seq_file *m)
static void blk_tracer_start(struct trace_array *tr)
{
- if (atomic_add_return(1, &blk_probes_ref) == 1)
- blk_register_tracepoints();
trace_flags &= ~TRACE_ITER_CONTEXT_INFO;
}
@@ -1107,15 +1105,10 @@ static int blk_tracer_init(struct trace_array *tr)
static void blk_tracer_stop(struct trace_array *tr)
{
trace_flags |= TRACE_ITER_CONTEXT_INFO;
- if (atomic_dec_and_test(&blk_probes_ref))
- blk_unregister_tracepoints();
}
static void blk_tracer_reset(struct trace_array *tr)
{
- if (!atomic_read(&blk_probes_ref))
- return;
-
blk_tracer_enabled = false;
blk_tracer_stop(tr);
}
@@ -1254,6 +1247,9 @@ static int blk_trace_remove_queue(struct request_queue *q)
if (bt == NULL)
return -EINVAL;
+ if (atomic_dec_and_test(&blk_probes_ref))
+ blk_unregister_tracepoints();
+
kfree(bt);
return 0;
}
@@ -1280,6 +1276,9 @@ static int blk_trace_setup_queue(struct request_queue *q, dev_t dev)
return -EBUSY;
}
+ if (atomic_inc_return(&blk_probes_ref) == 1)
+ blk_register_tracepoints();
+
return 0;
}